LAREDO, Texas — The gentle stream that usually marks the Rio Grande bulged into a mighty river along much of its southern reach Thursday as a rain-packed tropical depression dumped on a Texas-Mexico border region already struggling with flooded homes and evacuations after last week's hurricane.

Authorities in Laredo evacuated several neighborhoods close to the river and a 16-story hotel on the banks as the river grew to 42 feet deep and water began to creep into some homes. The tropical depression-driven rains were expected to keep the water level high, said city spokeswoman Xochitl Mora Garcia.

"It's difficult to describe," said Jerry W. Archer, the manager of Rio Grande Plaza Hotel. He estimated the river was about 15 times its usual size. "I was born and raised on the Mississippi River, but people here are used to just a small stream."

Eric Gay
/
AP

A trailer floats down the Rio Grande in Laredo, Texas, on Thursday.

The muddy waters — driven by dam releases upstream and rain-swollen tributaries following last week's Hurricane Alex — submerged light poles and towering palm trees, leaving only a few fronds waving above the water line.

National Guard troops arrived Thursday to help with evacuations, and people in low-lying areas were gathering sandbags to protect their homes before being forced to leave.

Nancy Castillo, 35, was picking up sandbags while her sister prepared to evacuate from her home near a dry creek bed that's overflowing with water that would normally head into the Rio Grande.

"It's typically dry everywhere in Laredo — except now," she said.

Tens of thousands of people had already been forced from their homes in Mexican towns earlier in the week as dam releases dumped torrents of water into flood-swollen rivers to avoid the risk of out-of-control releases following Hurricane Alex.

Humberto Moreira, the governor of the border state of Coahuila, said that more than 20,000 homes had been flooded in his state alone, and about 80,000 people had "lost all of their furniture." A similar number of people had their homes damaged in Nuevo Leon, said that state's Gov. Rodrigo Medina.

Gov. Eugenio Hernandez of the border state of Tamaulipas reported the first fatality there; telling an emergency evaluation meeting attended by President Felipe Calderon in the border city of Matamoros that the victim tried to cross a flooded road.

The tropical depression made landfall at South Padre Island late Thursday morning and was expected to dump four to eight inches of rain across the area, with as much as 10 inches in some parts, said the National Weather Service. That rain comes on top of the five to seven inches Hurricane Alex already had deposited.

In Laredo, where roughly half of all U.S.-Mexico trade crosses, authorities closed two bridges and severely limited traffic on a third. They also restricted traffic on the World Trade International Bridge to keep the weight load on the bridge at a minimum, but they did not have to close the connection.

The World Trade bridge carries roughly 8,000 18-wheelers a day, and closing it would have crippled the nation's busiest inland port.

Another worry for local officials was the half dozen tractor trailers that were bobbing downriver in the fast-moving current after being left too close to the rising water, said City Manager Carlos Villarreal.

"It's like a missile headed for a target," he said of the trailers' potential to damage the bridge structures.

Downstream in Rio Grande City, water from dam releases and the tropical depression were converging to create a serious flood threat.

The National Weather Service issued a flood warning for the area after the river more than doubled its normal size. Flooding would damage farmland and could push water from a creek along the eastern side of town into neighborhoods.

At the Retama Manor nursing home in Rio Grande City, administrators waited for local emergency officials to advise them of any risk posed by the Rio Grande. The facility sits next to the international bridge on the banks of the river, just feet from the swift-moving river.

Nan Impink, a spokeswoman for the facility, said there is a plan to move residents if there is a danger of flooding.

Farther south, part of the Rio Grande flow was being diverted into miles of wide channels that will eventually send some of the flow to the Gulf of Mexico.

The International Boundary and Water Commission said the last similar diversion happened after 1988's Hurricane Gilbert.

The IBWC has had to release water from the binational Amistad Dam at its fastest rate in a quarter century after the reservoir reached its highest level since 1974. Water was also being released at Falcon Dam downstream Thursday.

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Video: Texas braces for heavy rains

Transcript of: Texas braces for heavy rains

BRIAN WILLIAMS, anchor:There's some more bad weather to report tonight coming out of the
Gulf of Mexico
, and again right smack into
Laredo
,
Texas
, where four inches of rain have already soaked the ground, sent the
Rio Grande
into one of its highest levels in memory, and it's not over yet. Another three to five inches of rain could be coming over the next 48 hours.
Weather Channel
meteorologist
Mike Seidel
is in
Laredo
for us.
Mike
, it's great for
Louisiana
that these storms so far are taking a hard left. It's very bad for
Texas
.

MIKE SEIDEL reporting:It is, and tonight we're right here on the
Rio Grande
. We're on a road that leads to a shopping mall. The whole parking lot is underwater. In fact, we're watching the water coming up and lapping at our feet. Look at the mighty
Rio Grande
. Back on Sunday, it was only three feet deep and 50 yards wide. It's now 40 feet deep and stretches almost a half a mile. It's the third highest crest on record, expected to crest later tonight, begin to fall slowly on Friday. The reason for this, all the rain from
Hurricane Alex
and its aftermath, 20 to 25 inches of rain last week and into the weekend. Now, upstream in
Mexico
they're trying to protect their dams, so they're dumping a lot of water. And that's eventually ending up here in the
Rio Grande
. Three of the four bridges, including the one there behind me, are closed, including the
World Trade International Bridge
. That handles half of all
US-Mexican
trade. The bridges may be closed well into the weekend. Meanwhile, many on both sides of the border lined the banks today, amazed at how deep and how wide the river is. Two hundred mandatory evacuations on the
Texas
side. On the Mexican side, thousands have left their homes upstream in towns because of the dams. And tonight,
Brian
, we're concerned with more rainfall over the next couple of days.

WILLIAMS:Awful shame for the folks there in
Laredo
.
Mike Seidel
, thanks for that report.